Apparatus and method for picking up and transporting cloth pieces from a stack

ABSTRACT

AN APPARATUS AND METHOD OF PICKING UP INDIVIDUALLY PIECES OF CLOTH FROM A STACK THEREOF AND CARRYING THE INDIVIDUAL CLOTH PIECES AWAY FROM THE POINT OF PICKING UP AND DEPOSITING THEM INDIVIDUALLY ON A SUPPORT SUCH AS A CONVEYOR. THE INVENTION IS CHARACTERIZED BY ITS ABILITY TO PICK UP OR SEPARATE INDIVIDUAL CLOTH PIECES FROM THE STACK WITHOUT REMOVING THE NEXT UNDERLYING PIECE OR A PLURALITY OF SUCH PIECES. THE CYCLE OF OPERATION IS AUTOMATIC AND REPETITIVE.

United States Patent Eugene E. Stone, 111;

Walter L. Lynch, Jr.; Roger D. Barron, Greenville, S.C.

Nov. 8, 1968 June 28, 1971 Stone Manufacturing Company Greenville, S.C.

Inventors Appl. No. Filed Patented Assignee APPARATUS AND METHOD FOR PICKING UP AND TRANSPORTING CLOTH PIECES FROM A STACK 19 Claims, 32 Drawing Figs.

U.S. CI. 271/19, 271/1 1 Int. Cl B65h 3/22 Field of search 271/19, 20,

[56] Reierences Cited UNITED STATES PATENTS 793,009 6/1905 Miller. 271/18 1,920,388 8/1933 Harrold 271/30 2,147,099 2/1939 Jones 271/11 2,726,861 12/1955 Wolffetal 271/26 3,404,789 10/1968 Georgeffetal. 271/26 Primary ExaminerHarvey C. Hornsby Assistant Examiner-Joseph Wegbreit AttorneyB. P. Fishburne, Jr.

ABSTRACT: An apparatus and method of picking up individually pieces of cloth from a stack thereof and carrying the individual cloth pieces away from the point of picking up and depositing them individually on a support such as a conveyor. The invention is characterized by its ability to pick up or separate individual cloth pieces from the stack without removing the next underlying piece or a plurality of such pieces. The cycle of operation is automatic and repetitive.

PATENTEDJUH28IQ7! 3,588,091

Q 1 E 1 fi q- EUGENE E E 352 i? WALTER L: LYNCH, JR,

ROGER 0. BARRON ATTORNEY PATENTEU JUNE 8 I97! SHEET 02 [1F avco mun PATENTEU JUN28 I971 SHEET 03 HF PATENTED JUN28 19m SHEET nu 0F 10 PATENTED JUH28 I97! SHEET 05 [1F PATENTEUJUH28I97I 35 6,0531

sum as or 10 R HQM F I624 195 V THREAD] 1 H2 BREAK m I93 l s4 I we 4 RIAGE BACK HEADS RETURN T f M 1 l8! 2: I83 I Q3 +|2v 37 SV-S I84' I 7 TABLE woven i e W TABLE fi f SENSING WV H I 96 SWITCH I74 sv.4 1 I89 R FR CR 1 WE 9| 250 254 253 I76 SV-5 RR 255 W RRR W T I64 I77 FRONT TRAVEL I92 WV L -*-l END OF PATENTEDJUNZBM 3,588,091

SHEET OSUF 10 PATENTED JUN28 I97! SHEET 10 []F APPARATUS AND METHOD FOR PICKING UP AND TRANSPORTING CLOTH PIECES FROM A STACK BACKGROUND OF THE INVENTION The need for the invention arises in connection with the current move toward automation in the apparel industry or garment manufacturing industry. Before any complete satisfactory automation system can be devised, it is basic and essential that an extremely reliable means be made available for picking up one at a time pieces of cloth from a supported stack of cloth. Such stacks are produced by well-known techniques involving the laying down and subsequent cutting of long cloth spreads or lays on very large tables in the cutting room. In order for the pickup means to be practical and economical, it must have a high degree of reliability in separating a single piece of cloth from the topof the stack without picking up two or more pieces. One malfunction in 1,000 operation cycles is approaching the degree of reliability necessary to a profitable manufacturing operation. It is believed that the present invention apparatus and method will exceed this degree of reliability considerably.

The invention will find utility in a variety of stations in a garment or like article manufacturing system. For example, the pickup and transporting apparatus may be used in conjunction with a power hem folder and a sewing machine, which elements act upon the individual cloth pieces in succession as they are lifted from a stack and placed on a continuously moving conveyor upstream from the sewing station. Additional automation components and processing mechanisms may be included downstream from the sewing station and a plurality of the invention cloth pickup units may be employed at various points in a rather complete manufacturing system.

SUMMARY In essence, the invention includes an automatically adjustable support table for a stack of cloth pieces and a pair of overhead coacting pickup units which remove individually cloth pieces from the top of the stack. The pickup units embody heads having unique gripping fingers which constitute the heart of the invention, because these fingers unfailingly remove and lift one piece only of cloth from the top of the stack. Adjustments are provided for handling cloth having widely differing physical properties. One of the pickup units transports the individual cloth pieces away from the stack after such piece is released by the second unit and deposits each piece individually on a conveyor which carries the pieces downstream for automatic hemming and/or other processing. The cycle of operation is automatic and repetitive and electrically controlled.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a general side elevation of the invention apparatus.

FIG. 2 is an end elevation thereof.

FIG. 3 is a transverse vertical section on an enlarged scale taken substantially on line 3-3 of FIG. 1 with background parts omitted for clarity.

FIG. 4 is a fragmentary vertical section taken on line 4-4 of FIG. 3.

FIG. Sis a similar section taken on line 5-5 of FIG. 3.

FIG. 6 is a fragmentary vertical section taken on line 6-6 of FIG. 5.

FIG. 7 is a fragmentary vertical section taken on line 7-7 of FIG. 3.

FIG. 8 is a horizontal section on an enlarged scale taken on line 8-8 of FIG. 7.

FIG. 9 is an enlarged fragmentary vertical section taken on line 9-9 of FIG. 3.

FIG. 10 is a fragmentary vertical section taken on line 10-10 of FIG. 9.

FIG. 11 is a fragmentary horizontal section taken on line 11-11 ofFIG. l0.

FIG. 12 is a horizontal section taken on line 12-12 of FIG.

FIG. 13 is an enlarged transverse vertical section taken on line 13-13 of FIG. 1.

FIG. 14 is a horizontal section taken on line 14-14 of FIG. 13.

FIG. 15 is a transverse vertical section taken on line 15-15 of FIG. 1.

FIG. 16 is an enlarged fragmentary side elevational view, partly in section and partly broken away, showing the coacting pickup units and associated parts and the supporting structure for said units.

FIG. 17 is a side elevational view, partly in section, of carriage mechanism for the front movable pickup unit viewed from the side opposite to that shown in FIG. 16.

FIG. 18 is a partly diagrammatic view of a long stroke cylinder unit for moving the front pickup unit downstream from the cloth stack and the associated fluid control circuit for such cylinder.

FIG. 19 is an enlarged central vertical section through one pickup head of the apparatus.

FIG. 19a is a greatly enlarged fragmentary view showing the action of cloth pickup fingers.

FIG. 20 is a horizontal section taken on line 20-20 of FIG. 19.

FIG. 21 is a similar section taken on line 21-21 of FIG. 19.

FIG. 22 is an end elevation of the pickup head shown in FIG. 19.

FIG. 23 is a fluid circuit diagram showing the control valves and associated elements for the power components of the apparatus.

FIG. 24 is a schematic view of an electronic control circuit for the apparatus.

FIGS. 25 through 30 are partly diagrammatic action views of the front and rear pickup heads viewed in side elevation.

FIG. 31 is a fragmentary side elevational view of pickup units and associated parts in accordance with a modification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings in detail, wherein like numerals designate like parts, and referring in particular to FIG. 1, the apparatus in its entirety is shown in this FIG. including a main upstanding supporting frame 40 at the upstream end of the apparatus. This main frame 40 includes upstream and downstream corner posts 41 and 41' and top horizontal frame bars 42 at the sides of the frame 40 including downstream extensions 42' which project considerably beyond the downstream posts 41', as shown. Additional horizontal frame members 43 rigidly anchored to the posts 41 are disposed beneath and parallel to the bar extensions 42 and are interconnected therewith by vertical braces 44. Additional brace members are included in the frame structure, unimportant to an understanding of the invention, and these minor elements, some of which are shown in the drawings, need not be described in detail.

As will soon be apparent, the cloth pickup units which constitute very important components of the invention and the associated movable cloth stack supporting table and certain other elements to be described are all mounted on the main frame 40 and its downstream projecting extension. Beneath this extension, which includes the members 42 and 43, is a horizontal cloth power conveyor 45 of a conventional type, preferably including a plurality of spaced endless tapes whose upper runs carry the individual cloth pieces deposited thereon by the pickup means further downstream to a sewing machine 46 mounted on a suitable support 47, the conveyor 45 also having the necessary support frame structure 48. A suitable power folder mechanism 49 may be mounted directly upstream from the sewing machine 46 so as to receive an edge portion of each cloth piece and automatically fold such edge portion into a double fold hem for passage through the sewing machine which stitches the hem. The above is but one arrangement which may be employed in conjunction with the cloth pickup and transferring means on the main frame 40, now to be described in detail.

Near and below the top of the support frame and near the sides of the same are two parallel longitudinal fixed horizontal support bars for a rear or upstream pickup assembly or unit 51. The rear pickup assembly 51 is best shown in FIGS. 3 through 12 and 16 of the drawings and constitutes a vital component of the invention. The assembly 51 is suspended from the bars 50 by bushings 52 to the outer sides of which are rigidly attached plates 53 which extend vertically. An upper cross bar 54 extends between the plates 53 immediately under the bars 50, FIG. 3, and bearings 55 for a transverse horizontal rotary shaft 56 are supported on the plates 53 near their bottoms, FIG. 3.

The shaft 56 is powered through bevel gears 57 and 58 by a fluid operated rotary actuator 59 of a known type whose controls will be described. The shaft 56 carries spur gears 60 near its ends meshing with rack bars 61, held in suitable guides 62 on the plate means 53, FIGS. 4 and 5. At their bottoms, the rack bars 61 are secured to a horizontal support plate 63, FIGS. 3 and 12, which directly supports a rear or upstream pair of identical pickup heads 64, the construction of which contains the very heart of the invention. The pickup head 64 is shown in full detail in FIGS. 19 through 22 and a total of four such heads are employed in the invention, one pair of heads for the rear or upstream pickup assembly 51 and a second pair for the forward or downstream pickup assembly 65, yet to be described.

The pickup heads 64 of the rear assembly 51 are adjustable laterally on the support plate 63 to selected spaced positions through the medium of adjusting slots 66 and 67 in this plate, FIG. 12. Each pickup head 64 has a holder 68 equipped with an adjusting clamp screw 69 engaging through one of the slots 67 for securing the rear heads 64 in selected adjusted positions on the plate 63.

Referring now to FIGS. 19 through 22, one of the pickup heads 64 is shown in full detail, and comprises an internal axially movable sleeve 70 having its upper end secured to the reciprocatory rod 71 of a piston 72 contained within an air cylinder 73 having air inlet and outlet means in its top above the piston, downward movement of the piston being opposed by a spring 74. The lower end portion of the sleeve 70 is formed to provide a plurality, preferably four, circumferentially equidistantly spaced resilient fingers 75 having cloth gripping or pinching bottom terminals 76 whose external sides are conically tapered downwardly. The fingers 75 and terminals 76 are produced by right angular cross slots 77 formed through the fingers and terminals and these slots and the small flat faces 78 on the extreme lower ends of the terminals 76 are critical in the reliable picking up and removal of a single layer of cloth from a stack.

The interior sleeve 70 is surrounded by a first head member or housing part 79 having a bore 80 receiving the sleeve 70 with clearance. The head member 79 is secured fixedly at 81 to the lower end of air cylinder 73. A second and lower adjustable head member or housing part 82 surrounds the sleeve 70 and finger 75 and also has a clearance bore 83 having a downwardly conically tapered lower end portion 84 which engages the tapered finger terminals or gripping terminals 76 to adjust the same. When the piston 72 is displaced downwardly wit the sleeve 70, the reaction of the tapered surface 84 on the gripping terminals 76 will result in closing the same radially so as to pinch a layer of cloth preparatory to lifting the same from the stack of cloth.

When the elements 76 are fully opened, FIG. 19, and are pressed down against a stack of cloth, an upward bulge 85 from the topmost layer or piece 86 of cloth in the stack, FIG. 19a, is formed within the opening afforded by the cross slots 77. If this opening is set too narrowly. the cloth bulge 85 will be unable to enter the opening sufficiently and proper pinching or gripping of the cloth layer 86 will not occur when the extremities 76 are closed. When thick cloth is being handled, the size of the bulge 85 is greater and requires a greater spacing of the terminals 76 to properly grip a single layer of cloth and still not grip or pinch the next lowermost layer. When very thin material is encountered, the spacing of the terminals 76 when fully open will be substantially less to assure picking up a single layer only. Therefore, the initial setting of the opening afforded by the slots 77 must vary in accordance with the thickness and rigidity of the cloth. The precise setting must be determined by trial and error for each type of cloth being handled for best results.

To facilitate this rather critical adjustment, the upper head member 79 has a pair of spring-loaded detent pins 87, FIG. 19, adapted to enter selectively any diametrically opposed pair of a series of circumferentially spaced detent recesses 88 in the lower head member 82, which has a threaded connection at 89 with the upper head member ofthe pickup head. Consequently, the lower head member 82 may be backed off somewhat from the head member 79 to enlarge initially the width of the slots 77 and a full range of adjustment is provided by means of which a variety of cloth types may be handled.

The amount of downward pressure which must be applied to the cloth stack, FIG. 19a, to assure formation of the necessary bulge 85 and hence reliable picking up of a single cloth piece will depend to a great extent on the area of end surfaces 78. If too small an area, these surfaces will penetrate the cloth and if too large an area, excessive downward pressure is necessary. Again, the optimum area for the faces 78 is determined experimentally for different types of cloth and it is contemplated that several readily interchangeable pickup finger sleeves having different sizes of surfaces 78 will be made available with the apparatus for increased versatility. When properly adjusted, the pickup head 64 as described above will pinch and pickup a single layer of cloth from a stack with a high degree of reliability and this is absolutely essential to a profitable commercial adaptation of the invention. As previously mentioned, each of the four pickup heads 64 of the apparatus is identical to the others and therefore the above detailed description of one head per se will serve to describe all of the heads.

Returning to the rear pickup assembly 51 in FIGS. 3 through 12, also mounted adjustably on the plate 63 between the heads 64 is a cloth stack sensor 90 having a vertical sensing pin 91 which directly contacts the top of the cloth stack 92 having the individual layers 86 mentioned in connection with FIG. 19a. The pin 91 projects above the plate 63 and contacts a pivoted spring-loaded rocker arm assembly 93 having an adjustment 94 and engaging the roller 95 on the actuator of a microswitch 96 also anchored to the support plate 63, FIG. 9. The rocker arm assembly 93 is pivoted at 97 to a suitable bracket 98 on the plate 63, as shown. The functioning of this sensor unit 90 will be dealt with further when the operation of the apparatus is summarized.

Also forming a part of the rear pickup assembly 51 is a cloth holddown unit 99, FIG. 3, suspended from a bracket 100 attached to the cross bar 54. The details of the holddown unit 99 are best shown in FIGS. 7 and 8. The unit includes a vertical plate 101 secured rigidly to the bracket 100, to which a bearing 102 for shaft 56 is attached. On the other side of this plate, a spur gear 103 is mounted on the shaft 56 and keyed thereto by a longitudinal key 104 on the shaft which extends continuously therealong. Thus, the gear 103 will turn with the shaft 56 but can be shifted axially to any desired position along the shaft. A holddown rack bar 105 is in mesh with the gear 103 and depends from the unit 99 generally vertically and is quipped at its lower end with a cloth holddown foot 106. The rack bar 105 operates within a guide 107 also secured to the plate 101. The guide 107 carries a projecting adjustable stop element 108 which engages one face of the gear 103 to assure its movement along the shaft 56 with the rest of the unit 99 when such adjustment is required. The entire unit 99 is shiftable anywhere along the shaft 56 by simply loosening the clamp screw 109 which extends through a longitudinal slot 110 in the cross member 54, and then retightening this screw to secure the unit 99 in any selected adjusted position relative to the stack 92 and the pickup heads 64 of rear assembly 51. Different placements of the foot 106 are required somewhat dependent on the size and shape of the cloth pieces in the stack 92 and their placement on the support table yet to be described, and on other factors.

Also on the rear pickup-assembly 51 is a rotary cam 111 on the end of shaft 56 remote from gear 57 and turning with the shaft 56. A table motor control microswitch 112 is mounted on a small bracket, attached to the plate 53 above the cam 111, whereby this cam can actuate the switch 112 on each complete revolution of the shaft 56. The cooperation between the sensor 90 and its switch 96 and the cam and switch 111 and 112 will be further described.

The entire assembly 51 may be adjusted as required forwardly and rearwardly along the support bars 50 and locked in the selected adjusted position by a clamp unit 113, FIGS. 5 and 6, having a clamping screw 114 and a connecting link 115 with the assembly 51.

Beneath the rear pickup assembly 51 is a vertically movable cloth support table 116, having a frame 117 upon which a base plate 118 of plywood is mounted, FIG. 3, a second layer of medium-firm sponge rubber 119 and a top layer 120 of heavy felt which receives the cloth stack 92. This particular table construction has proven necessary. It permits reliable picking up of the last few plies of cloth; it prevents cutting or piercing the cloth against a hard surface as the last few plies are picked up. In general, the table structure is made to simulate closely the physical characteristics of the cloth stack with which the pickup fingers 75 are designed to function with a high degree of reliability in picking up a single layer only of cloth, as described.

The table frame 117 carries vertical guide sleeves 121, FIG. 2, slidable on vertical guide posts 122 at the upstream end of the main frame 40 inwardly of posts 41. Stop elements 123 are secured to the vertical guide posts 122 to positively limit downward movement of the table 116. The table is raised in response to the coaction of switch 112 and associated circuitry by an electric drive motor 124 on the base of main frame 40 operatively connected through reduction gearing 125 with a vertical drive shaft 126 having drive screw portion 127. Affixed to the table frame 117 is a manual drive clutch 128 having a spring-biased plunger 129 engaging screw 127 and being manually retractable when it is desired to return the table quickly to its lowered position. The normal engagement of the plunger 129 with the screw 127 causes the gradual elevation of the table when the screw is driven in the proper direction.

Vertical stack positioning rods 130 are secured at their lower ends to a longitudinal support member 131 on one side of the main frame 40, FIGS. 1 and 3. The rods 130 are stationary and are received through clearance openings in the table structure so that the table may move vertically freely relative to these rods. The individual rods 130 are positioned most advantageously in an oblique row for engagement with one edge of the cloth stack 92 on the table. This simply assures proper positioning ofthe stack initially.

Another feature is the provision on the top of the table of flattened apertured pipes 132, FIG 1, through which suction is created from below through a suitable hose 133 leading to a vacuum source, not shown. The purpose of this suction arrangement is to apply suction to the bottom of the cloth stack to prevent movement thereof horizontally on the table particularly when the stack is depleted down to the last few pieces of cloth.

The apparatus further includes the already-mentioned forward or downstream pickup assembly 65 which cooperates with the rear assembly 51 in removing individual cloth pieces 86 from the stack 92. As will be described, the front pickup assembly 65 also transports the individual cloth pieces downstream and deposits them in succession on the conveyor 45, after release by the rear pickup heads 64. The details of the front pickup assembly 65 and its carriage means for transporting it horizontally downstream and rearwardly are best depicted in FIGS. 13 through 17.

In these FIGS. the front pickup unit 65 comprises a horizontal support plate 134 for a pair of the pickup heads 64 which have been previously described in detail in connection with FIGS. 19 to 22. The plate 134 is similar to the support plate 63 for the rear pickup heads and is slotted a 135 and 136 so that the individual heads 64 may be adjusted laterally of the plate with their respective holders 137 and 138. As shown in FIGS. 14 and 16, the heads 64 of the forward pair are preferably staggered or offset longitudinally of the apparatus to accommodate cloth which is nonrectangular more efficiently. This arrangement may be varied. The plate 134 and the heads 64 on it are bodily carried on a sturdy vertical member 139 whose lower end is hinged to the plate 134 at 140. The suspension plate 139 forms part of a carriage structure for the forward pickup assembly 65 which is capable of moving horizontally downstream and upstream relative to the cloth stack 92. To facilitate this, a central horizontal guide bar 141 is provided and has its ends carried by the downstream end of the main frame extension including elements 42, 43 and 44 and by a cross member 142 adjacent the posts 41 of the main frame. The upper end of suspension plate 139 has a sleeve 143 receiving guide bar 141 slidably and a stabilizing extension arm 144, FIG. 15, rigid with the plate 139, extends beyond one side thereof and carries another sleeve or bushing 145 slidable upon another horizontal guide bar 146 parallel to the bar 141 and coextensive therewith. The upstream end of guide bar 146 is supported from the cross member 142 by a hanger bracket 147 while its downstream end is supported by the projecting main frame extension, as shown in FIG. 16. The two guide bars 141 and 146 and the arm 144 prevent lateral swaying or pivoting of the vertical member 139 which carries the front pickup assembly 65.

The front pickup assembly further includes a diagonal extensible and retractable cylinder/piston unit 148 having its lower piston rod end pivotally secured at 149 to a bracket 150 rigid with the support plate 134. Extension and retraction of the cylinder/piston unit 148 causes raising and lowering of the front pickup assembly 65 on the axis of the hinge or pivot 140, as show in FIGS. 25--28. The top end of the unit 148 is pivotally connected at 151 to the member 139 near the top of the latter.

Side vertical bars 152 are secured rigidly to the opposite sides of member 139, FIG. 15, and are connected rigidly at their tops by a short crosspiece 153 supporting a connector block 154 which is securely attached to a drive cable 155 of a horizontal longitudinal long stroke cylinder 156 containing a single piston 157 also fixedly secured to the endless cable 155 which moves about guide pulleys 158 at the ends of the long stroke cylinder.

A long horizontal support rail 159 for the cylinder 156 and associated elements is located at the transverse center of the apparatus and extends longitudinally for substantially the length of the main frame 40 near the top thereof, as shown in FIG. 1. Intermediate its ends, the rail 159 is securely clamped to cross member 142 as at 160, FIG. 13. Its upstream and downstream ends are also firmly connected to the main frame structure, the details of which connections are unimportant. As shown in FIGS. 3 and 16, supports 161 for the upstream and downstream pulleys 158 are rigidly mounted on the rail 159. Side supporting plates 162 on opposite sides of the long stroke cylinder 156 and above the rail 159 are also included in the fixed overhead support structure for the cylinder and associated elements and these side plates are attached to the vertical supports 161 on rail 159 forming a boxlike structure around the cylinder 156.

Referring to FIG. 15 in particular and also to FIGS. 16 and 17, the elements 139, 144, 143, 145, 152 and 153 must all move relative to the fixed rail 159 and other fixed parts of the apparatus. The elements 152 and 153 straddle the top of the fixed rail 159, FIG. 15, while the top end of member 139 is beneath this rail, thus allowing the entire carriage structure for the front pickup assembly 65 to travel upstream and downstream on the guide bars 141 and 146 without interference with fixed members. This movement is caused by movement of the piston 157 and the cable 155 which connects to the element 154 in turn secured to the crosspiece 153 of the carriage structure.

A pair of cams 163 is mounted at the opposite sides of bars 152 fixedly, FIG. 15, under and just outside of the plates 162. These cams move along the guide bars 141 and 146 with the above-described carriage structure for the front pickup as sembly 65. Their purpose is to operate control switches 164 and 165, longitudinally adjustably mounted on one of the side plates 162 near the downstream end of the apparatus as best shown in FIG. 17. As will be fully described, the switch 164 dictates the releasing of each cloth piece by the pickup heads 64 of the front assembly 65 so that the cloth piece is deposited on the conveyor 45. The switch 165 dictates the reversal or upstream return movement of the front pickup assembly 65. As shown in FIG. 17, these switches are adjustable on the side plate 162 by virtue of an adjusting slot 166 formed therein. Also adjustably mounted on the two side plates 162, FIGS. 16, 17 and 18, are fluid flow controllers 167 having actuators 168 also in the path of movement of the two cams 163. As will be explained, these controllers 167 form part of a control system for the piston 157, FIG. 18, particularly to eliminate shock caused by the abrupt reversal of the long stroke piston.

An upstream limit switch for the carriage of front pickup assembly 65 is also mounted as indicated at 169 on the side plate 162 carrying the switches 164 and 165. This limit switch has an actuator 170 in the path of travel of an abutment element 171 on one of the bars 152, see FIG. 15. The switch 169, as will be further described, when actuated halts the return movement of the front pickup assembly 65 and conditions the control circuitry for another cycle of operation.

Mounted on the top of frame bars 42 at the upstream end of the main frame is a housing 172 within which are supported solenoid-operated valves 173, 174, 175, 176 and 177, FIG. 23, for controlling the flow of pressurized air or other fluid to the rotary actuator 59 of the rear pickup assembly 51, the cylinders 73 of both the rear and front pickup assemblies 51 and 65, to the cylinder 148 of the front pickup assembly and to the long stroke cylinder 156, all shown in FIG. 23. The operation of this fluid system including the solenoid valves 173177 will be further described in connection with the overall control circuit of FIG. 24 and the action views in FIGS. 2530.

OPERATION The operation of the invention and the practice of the method can best be understood by reference to FIGS. 18 and 23 through 30.

Reference is made first to the action views of the rear and front pickup heads in FIGS. 25 to 30 for a brief summary of the essence of the operation. In FIG. 25, the cloth stack 92 is being supported at the proper elevation by the table 116. The rear and front pickup assemblies 51 and 65 are both raised and inactive while the holddown foot 106 is lowered and pressing against the top of the stack. The front pickup assembly 65 is in the rearmost or upstream position.

In FIG. 26, the rear and front pickup assemblies have descended substantially simultaneously and the holddown foot 106 has been raised from the cloth stack and the heads 64 of the rear assembly 51 are activated so that the pickup fingers 75, FIG. 19, will pinch or grip a single layer of cloth as shown in FIG. 19a.

In FIG. 27, the rear pickup assembly 51 has elevated and lifted the top cloth piece 86 from the stack 92 and the front pickup heads 64 of front assembly 65 have been activated and are pinching the same layer of cloth but not yet lifting the same from the stack. The holddown foot 106 has descended simultaneously with the raising of the assembly 51 and has flicked the rear end of the lifted cloth piece 86 and again engaged the top of the stack 92. This flicking action by the foot 106 on the rear portion 178, FIG. 27, will aid in separating a second piece of cloth, should a second piece of cloth tend to cling to the bottom of the single piece 86 being lifted by the rear pickup heads 64. At this point, an optional refinement may be included in the form of a blast of air directed in the vicinity of the rear pickup heads 64, FIG. 27, further tending to separate a second layer which might cling to the bottom of the layer 86 being lifted.

Proceeding to FIG. 28, the holddown foot 106 remains active on the top of the stack and the rear pickup heads 64 are in the up position and the front pickup heads 64 of assembly 65 have now been raised by the cylinder 148 and are lifting the forward part of the top cloth piece 86 from the stack. The assembly 65 is still remaining in the full upstream position relative to the stack 92. When all of this has occurred, FIG. 28, the rear pickup heads 64 will release the lifted cloth piece 86 which immediately tends to drop, as shown by the broken line. The front pickup heads 64 are still pinching and holding the cloth piece 86.

In FIG. 29, the rear pickup assembly 51 remains unchanged from its condition in FIG. 28 while the front pickup assembly 65 is moving downstream with its carriage structure on the guide bar 141 and is carrying the single cloth piece 86 with it to the conveyor 45.

FIG. 30 again shows no change for the rear pickup assembly 51 while the front assembly 65 is now fully downstream and responsive to the operation of switch 164; the front pickup heads 64 have released the cloth piece 86 for placement on the conveyor 45. The front assembly 65 will continue until the abutment 171, FIG. 15, actuates the limit switch 165 to reverse the movement of the assembly 65 by operation of the long stroke cylinder 156 and associated elements. The limit switch 169 upstream in FIG. 30 will stop the return movement of the assembly 65 and the parts will then be at the initial condition shown in FIG. 25 ready for another automatic cycle of operation.

For a more detailed understanding of the above operation, reference must be made to FIGS. 23, 24 and 13. In FIG. 24 showing the solid state control schematic, a primary power source of 220 volts AC coupled with a positive l2 volt DC power source, not shown, supplies positive l2 volts potential to the terminals of the solid state circuit, as shown in FIG. 24. In this figure, assume a condition of power off and the main power switch, not shown, open. In this condition, the holddown rack 105 is down and the racks 61 of rear pickup heads are up, as these components 105 and 61 operate reciprocally or reversely due to rotation of the concentric gears 60 and 103, FIGS. 3 and 8. The front pickup heads 64 are elevated and the apparatus is in the position depicted in FIG. 25.

When the main power switch, not shown, is turned on, 12 volts DC is applied to the control circuit of FIG. 24. To start the machine operation, a start switch 179 is closed and current is supplied to the trigger circuits of silicon controlled rectifiers (SCR) 180 and 181. Transistors 182 and 183 have been turned on through table elevation sensing switch 96. The two solenoid valves and 173 are energized, actuating cylinder 148 and rotary actuator 59, respectively, driving both the front and rear pickup assemblies 65 and 51 downward to their positions in FIG. 26.

If the table 116 is not up to the proper level to allow the pickup heads 64 to grasp a piece of cloth,-the table elevation sensing switch 96 will remain in the position shown in FIG. 24. When the pickup assemblies are lowered, FIG. 26, the switch 112 is closed by cam 111 on shaft 56, turning on triac 184, actuating relay 184' to start the table elevating motor 124. The table 116 now rises due to the action of screw 127 and the table will rise until the sensing plunger 91, FIG. 9, is engaged by the stack 92 for moving the table sensing switch 96 from its position in FIG. 24 to the opposite terminal shown therein. This deactivates the table drive motor 124.

As an alternative to manually lowering the table 116 by retracting plunger 129 from screw 127, this mechanical engagement may remain active and the table may be lowered by simply pressing spring returned reversing switch 250, which activates reversing relay 251 through switch 250, and motor start relay 184' through switch 252. Limit switches 253 and.

254 protect the table screw mechanism in the event that table motor 124 is driven too far.

Transistors 182 and 183 are turned off after a slight time delay to allow proper pinching of the top piece of cloth by the fingers 75. This time delay interval is set by the RC networks capacitor 185, resistance 186 and capacitor 187 and resistance 188, respectively. When this delay time, approximately 0.2 seconds has elapsed, the rear pickup assembly 51 rises, bringing up with it the rear end of the single piece of cloth 86, as shown in FIG. 27. At this time, the front pickup assembly 65 is still down against the cloth stack and remains down until the rear assembly 51 is fully elevated and the holddown foot 106 is again clamping the stack 92.

Regressing now to the time at which table sensing switch 96 transferred, SCR 189 and SCR 255 are thereby turned on, energizing solenoid valves 174 and 176, FIG. 23, causing the pinch fingers 75 of the front and rear pickup heads 64 to pinch or grip the cloth piece 86 by the operation of the cylinders 73 of the heads. The time delay in lifting the heads 64 is introduced to allow the fingers 75 to properly pinch the cloth, as stated.

When the front and rear pickup heads 64 are in the up position with the single cloth piece 86, FIG. 28, and the stack clamping foot 106 is down, switch 190 opens and the fingers of pickup heads 64 of rear assembly 51 release the cloth piece 86 as indicate by the dash line in FIG. 28. When SCR 189 turns off, the positive voltage rise at the anode will be coupled through capacitor 191 to turn on SCR 192, energizing solenoid valve 177 and thereby actuating long stroke cylinder 156 in the forward or downstream direction. This causes the front pickup assembly 65 to carry the cloth piece 86 over the conveyor 45, FIG. 29. When the assembly 65 travels the proper distance, one of the cams 163, FIG. 17, opens switch 164, opening the pinch fingers 75 of the front pickup heads 64 and dropping the cloth piece 86 on the conveyor or other work station. When the assembly 65, FIG. 30, moves slightly further downstream, the cam 163 operates limit switch 165, thereby deenergizing solenoid valve 177, and the piston 157 of long stroke cylinder 156 reverses and returns the front assembly 65 to its upstream position, which is the position shown in FIG. 25. When the front assembly 65 thus returns, the abutment 171 closes limit switch 169 and feeds a momentary pulse through capacitor 193 to SCR 180 and SCR 181, starting the cycle over again.

If, at any time during the operating cycle, it is desired to stop the apparatus by pressing the stop switch 194 or because of operation of sewing thread break switch 195, SCR 196 is turned on, which causes transistor 197 to conduct, grounding the signal path at the resistance 198, 199 and 200 junction, preventing the next operating cycle. The cycle, once started, will continue to completion. To start the apparatus again, start switch 179 is pressed, turning off SCR 196 and starting the cycle as before.

Transistor 201 serves only to prevent the actuation of solenoid valve 177 prematurely when the main power switch, not shown, is turned on. A positive pulse through capacitor 202 turns transistor 201 on momentarily, grounding the signal path from capacitor 191 to the gate of SCR 192.

Several important refinements of the invention have yet to be described, although the above completes the general description of operation.

For example, as shown diagrammatically in FIG. 16 only, a photoelectric cell 203 may be positioned below the table 116 and the latter may have a through opening 204 at its center normally covered by the cloth stack. A source of light 205 may be arranged overhead on a fixed structural element, such as the member 159. If the cloth stack 92 should become completely exhausted, exposing the photoelectric cell 203 to light from the source 205, the energizing of the cell would automatically stop the machine. This is an optional feature.

Another refinement, referring to FIGS. 19 and 23, resides in the direction of compressed air jets into the lower portion of the bores 83 of pickup heads 64 of front pickup assembly 65. The purpose of this is to dislodge any cloth piece which might tend to adhere between the pinching terminals 76 of the pickup fingers at the time of release, FIG. 30. This may be accomplished by connecting fluid lines 206, FIG. 23, radially into the lower pickup head sections or housing sections 82. These lines 206 lead to a flow valve 207 communicating with solenoid valve 175, as shown.

An important refinement is depicted in FIG. 18, which FIG. is included diagrammatically above the long stroke cylinder 156 in FIG. 23. In FIG. 18, flow lines. 208 and 209 are shown leading from and to the solenoid valve 177, which controls the operation of long stroke piston 157. A pair of spool valves 210 and 211 are provided having axially shiftable spools 212 and 213. Adjustable needle valves 214 and 215 are connected with the spool valve housings so that their connecting lines 216 can be closed when the spools 212 and 213 are positioned upwardly as in FIG. 18. Additional lines 217 and 218 lead from the spool valve chambers 219 and 220 into opposite ends of the long cylinder 156, on opposite sides of long stroke piston 157. The aforementioned flow controllers 167 or valves operated by the movable carns 163 of front pickup assembly 65 are connected by lines 221 and 222 to the tops of spool valves 210 and 211. Return lines 223 and 224 lead from the bottoms of spool valves 210 and 211 back to the flow controllers 167 through connectors 225 which also communicate with the main lines 208 and 209 leading to the valve chambers 219 and 220.

The purpose of this arrangement is to eliminate shock force on the piston 157 and cable at the moment when the movement of the piston is reversed in either direction and hence eliminate shock on the front pickup assembly 65. Continuing to refer to FIG. 18, air may flow from the solenoid valve 177 through lines 208 and 217 to the upstream end of long cylinder 156 to move the piston 157 to the right, which actually causes the cable 155 to move the pickup assembly 65 to the left or upstream in FIG. 1. Simultaneously, air exhausts from the remote end of cylinder 156 through line 218, chamber 220 and line 209, back to solenoid valve 177. At this time, no air can escape from the chambers 219 and 220 through the adjustable needle valves 214 or 215 and the flow controllers 167 are so adjusted that the spools 212 and 213 are positioned upwardly in FIG. 18. However, when the cams 163 strike the actuators 168 of flow controllers 167, these elements are conditioned so that pressurized fluid from the main lines 208 and 209 may enter the tops of the two spool valves 210 and 211 and drive the spool elements 212 and 213 downwardly, thus placing the chambers 219 and 220 in communication with the lines 216 and needle valves 215. Immediately, some air escapes from the system through these needle valves and the net effect is the dampening or cushioning of the piston 157 at the time that it stops and reverses its travel near one end of the long cylinder 156.

When air is entering the spool valves 210 and 211 in the opposite direction from the solenoid valve through the line 209 so as to drive the piston 157 to the left in FIG. 18, thereby moving the pickup assembly 65 downstream in FIG. 1, air will be exhausting through line 217, chamber 219 and line 208 and the needle valves 214 and 215 will be inactive until once again the cams 163 actuate the flow controllers 167 and produce through the needle valves the identical cushioning action of the piston 157 at the other end of its stroke. Without this arrangement, there is quite a severe shock on the piston at the time of reversal.

In FIG. 31, there is shown modification of the invention particularly constructed to handle cloth having a heavy nap, such as corduroy. This heavy nap cloth, when laid face-to-face in a stack, causes adjacent plies to cling together and it is more difficult to pick up a single piece or ply than in the case of sheer unnapped cloth. The purpose of the modification in FIG. 31 is to reduce and overcome this clinging effect present in certain types of cloth.

Referring to FIG. 31, the cloth stack is shown at 226 on the table 116, previously-described. A rear pickup assembly of modified form is indicated at 227 and the front pickup assembly 228 remains substantially identical to the previouslydescribed assembly 65 and includes supporting means 229 connected with and moved by endless cable 155, as described. The front pickup unit is adapted to travel horizontally on guide bar means 230 as in the prior embodiment and the assembly 228 has a hinged support plate 231 for pickup heads 232 whose details may be the same as for the head 64 shown in FIG. 19, it being understood that FIG. 31 is somewhat diagrammatic and eliminates some of the parts previously described for simplicity. The assembly 228 also includes a power cylinder 233 for raising and lowering the front pickup heads 232. In general, the front pickup assembly 228 and the table 116 operate in exactly the same manner as previously described, and the change involved concerns the rear assembly 227.

The rear assembly 227 comprises a pair of pickup heads 234 substantially identical to the heads 64, mounted on a hinged support plate 235 adapted to be raised and lowered by a power cylinder 236 similar to the cylinders 233 and 148. Another power cylinder 237 is carried by the supporting carriage means 238 of the rear pickup assembly and operates a pivoted stack holddown arm 239 which swings vertically between active and inactive positions relative to the cloth.

The entire rear pickup assembly 227 is supported adjustably on the guide bar means 230 and may be clamped in selected positions by clamping means 240 very similar to the means 113 of the prior embodiment.

A third power cylinder 241 interconnects the stationary clamp means 240 with the support and carriage means 238, which carriage means includes a sleeve 242 shiftable longitudinally on guide bar means 230 under influence of power cylinder 241 when the same is extended and retracted.

The mode of operation of the modified structure in FIG. 31 is as follows. Generally, the sequence of operations between the front and rear pickup assemblies 228 and 227 is the same as illustrated and described in FIGS. 30 and the steps need not be repeated in detail. However, in the modification, after the cloth pinching elements 76 of the front and rear pickup heads 232 and 234 have closed and the cloth has been lifted as in FIG. 28, the following takes place. The entire rear assembly 227 moves forwardly toward the front assembly 228 by retraction of cylinder/unit 241. This produces a peeling action between the top cloth ply being lifted and a second ply tending to adhere thereto and the action serves to overcome the nap bond, reducing the possibility of picking up two plies.

Proceeding to the situation of FIGS. 28 and 29, when the rear pickup heads 234 release the cloth piece so that the forward heads may carry it to the conveyor 45, the following takes'place. The power cylinder 241 quickly extends a short distance causing backing up of the assembly 227 while the pickup fingers of the front heads 232 are gripping the cloth and the fingers of the rear heads 234 are open. Should there be sticking of the heavier cloth in the rear pickup heads 234, this reverse snap-back action of the rear assembly 227 caused by power cylinder 241-will assure separation of the cloth piece from the rear pickup heads. Therefore, the additional cylinders 241 serves two purposes, namely, to peel or separate two cloth plies which may adhere when being picked up and later to insure release of the cloth cleanly from the rear pickup assembly. As in the prior embodiment, the front heads 232 may include the air jet producing means 206 of the prior embodiment for the stated purpose of preventing cloth from sticking or jamming in the pickup fingers.

Concerning this air jet feature on the front pickup heads in the modification, FIG. 31, and in the prior embodiment, it might be mentioned that the air jet feature is not needed on the rear heads of the apparatus because the front pickup heads, FIGS. 28 and 29, in all cases will serve to positively pull or dislodge any sticking cloth piece from the rear heads without difficulty.

The sequence of operations for the various power cylinders 236, 237 and 241 will be under control of solenoid valves and conventional control circuitry along the lines of the circuitry in FIG. 24. It is thought to be unnecessary to described in detail the additional'control means for a proper understanding of the modification.

The numerous advantages of the present invention over the prior art should now be readily apparent without any further description.

It is to be understood that the forms of the invention herewith shown and described are to be taken as preferred exarnples of the same, and that various changes in the shape, size and arrangement of parts may be resorted to, without departing from the spirit of the invention or scope of the subjoined claims.

We claim:

1. An apparatus for handling cloth pieces individually comprising support means for a stack of cloth pieces adapted to position the top cloth piece of the stack at a certain elevation, independently operable first and second pickup assemblies above the stack and support means, each pickup assembly including at least one pickup head and power means to raise and lower such head relative to said stack, a power-operated cloth gripping unit on each pickup head adapted to engage and grip the top cloth piece on the stack and to subsequently release said piece, said unit including plural circumferentially spaced mechanical gripping fingers and cam means to contract said fingers radially while their tips are in engagement with the top cloth piece, additional power means connected with the first pickup assembly to move the same away from the second assembly and stack, whereby said top cloth piece is carried by the first pickup assembly to a remote station, and control and timing means for said power means, power-operated gripping units and said additional power means operable to cause the second pickup assembly to first pick up a rear end portion of the top cloth piece followed by picking up of the front end portion of such piece by the first pickup assembly and later the release of the rear end portion by the second pickup assembly prior to the first assembly carrying the top cloth piece to said remote station.

2. An apparatus as defined by claim 1, and an additional pickup head on each pickup assembly substantially identical to the named head of each assembly, and adjustable supporting means for the heads of each assembly enabling the distance between the heads of each assembly to be adjusted readily.

3. An apparatus for handling cloth pieces individually comprising support means for a stack of cloth pieces adapted to position the top cloth piece of the stack at a certain elevation, independently operable first and second pickup assemblies above the stack and support means, each pickup assembly comprising a pair of pickup heads, adjustable supporting means for the heads enabling the distance between the heads to be varied readily, and power means to raise and lower the heads of each assembly in unison, power-operated cloth gripping elements on each pickup head comprising plural circumferentially spaced radially expansible and contractable gripping fingers whose longitudinal axes during use are substantially normal to the plane of the stack and whose bottom terminals contact the top cloth piece on the stack prior to the activation of said fingers for gripping and picking up the top cloth piece, additional power means connected with the first pickup assembly to move the same away from the second assembly whereby said top cloth piece may be carried by the first pickup assembly to a remote station, and control and timing means for said power means, power-operated gripping elements and said additional power means.

4. In an apparatus for handling individual cloth pieces in a stack, a pickup head, said pickup head comprising an inner axially movable pickup member having at least three circumferentially equidistantly spaced resilient gripping fingers at its leading end, said fingers having camming surfaces, a housing member substantially surrounding said pickup member and fingers and having a coating camming surface engaging said camming surfaces of the fingers, said fingers including leading tips which project forwardly of the leading end of the housing member, the housing member and said inner pickup member being substantially coaxial, and power means connected with the pickup member to shift it axially relative to the housing member so that the coacting camming surfaces will produce radial contraction or expansion of the gripping fingers.

5. The structure of claim 4, and wherein said housing member is formed in two parts having a threaded connection whereby the axial location of said coacting camming surface may be adjusted relativeto the camming surfaces of the fingers, and detent means releasably locking said two parts of the housing member in selected adjusted positions.

6. The structure of claim 5, and conduit means connected with the interior of the housing member adjacent said fingers so that an air jet stream may be introduced near the fingers to aid in releasing a cloth piece held by the fingers.

7. The structure of claim 4, wherein said camming surfaces are on forward terminals of the fingers and said surfaces collectively define a conical camming surface and said coacting camming surface being conical and concentric with the firstnamed conical surface.

8. An apparatus for handling cloth pieces comprising an ad justable table support for a stack of cloth pieces, a first pickup assembly including plural cloth pickup heads arranged above the table support, each pickup head including a circumferentially spaced grouping of radially contractable and expansible mechanical pickup fingers and power means to operate said fingers, overhead support means for the first pickup assembly, power means on the first pickup assembly to raise and lower the pickup heads thereof in unison, a stack clamping member on the first pickup assembly also operated by the power means reciprocally to the pickup heads, a second pickup assembly above said table support including plural cloth pickup heads, each pickup head of the second assembly including circumferentially spaced grouping of radially contractable and expansible mechanical pickup fingers and power means to operate said fingers, overhead support means for the second pickup assembly including substantially horizontal guide means extending away from the table support, power means on the second pickup assembly operable to raise and lower the pickup heads of the second assembly in unison and independently of the pickup heads of the first assembly, and additional power means connected with the second pickup assembly capable of moving it in opposite directions on said guide means.

9. The structure of claim 8, wherein said additional power means comprises a long stroke substantially horizontal cylinder/piston unit on the overhead support means having a positive connection with the second pickup assembly.

10. The structure of claim 9, wherein said positive connection includes an endless flexible driving element connected with the piston of the cylinder/piston unit and an element on the second pickup assembly secured to the endless flexible element for movement therewith.

11. The structure of claim 10, and a fluid circuit having a connection with the cylinder of the cylinder/piston unit near its opposite ends and control valve means in the fluid circuit operated by movement of the second pickup assembly on the horizontal guide means for cushioning the piston of the cylinder/piston unit at the moment when the piston reverses its movement.

12. The structure ofclaim l1, and cam means on the second pickup assembly engaging and operating said control valve means during movement of the second pickup assembly.

13. The structure of claim 8, and control switches on the overhead support means engaged and operated by movement of the second pickup assembly along said guide means, said switches controlling the stopping and reversing of the second pickup assembly on said guide means and the releasing of cloth pieces by the pickup heads of the second pickup assembly.

14. The structure of claim 4, wherein said gripping fingers are four in number and equidistantly spaced circumferentially and have leading tips whose outer sides are conically tapered and whose interior sides are arranged substantially at right angles, whereby the four gripping fingers define intersecting substantially right angular cross slots between them, said slots collectively forming a central opening into which the pinched single piece of cloth is received when the cloth is bulged upward ly by radial closing of the fingers, the fingers having substantially flat leading end faces preventing them from puncturing the cloth.

15. The structure of claim 8, wherein the power means on the first pickup assembly comprises a rotary actuator, a rotary shaft driven by said actuator, a support member for the pickup heads of the first pickup assembly, gearing interconnecting said support member and shaft whereby turning of the shaft by said actuator raises and lowers the support member and pickup heads, a second support member on the first pickup as sembly, gearing carried by the second support member and having a splined connection with said shaft and turned thereby and being axially adjustable along the shaft and second support member, and said stack clamping member connected with and raised and lowered by the gearing on the second support member.

16. A method of handling individual cloth pieces in a stack comprising the steps of applying a clamping force to the top of the stack, engaging the top of the stack near first and second ends thereof with mechanical pickup finger units and substantially simultaneously releasing the clamping force on the top of the stack, gripping the top cloth piece only of the stack at the points of engagement by the finger units and lifting only the first end portion of said top cloth piece and reapplying the clamping force to the top of the stack substantially as the first end portion of the top cloth piece is lifted, thereafter lifting the second end portion of the top cloth piece so as to elevate the entire piece from the stack, releasing the first end portion of the top cloth piece while continuing to support the second end portion and carrying the top cloth piece away from the stack by dragging it substantially horizontall at said lifted second end portion, and then releasing the second end portion of the top cloth piece for depositing the piece at a location away from the stack.

17. A method of picking up a single layer of cloth from a stack containing multiple layers comprising supporting said stack, engaging the top of the stack with plural circumferentially spaced radially movable pickup elements having blunt leading ends while the elements are spread apart and applying pressure to the stack through said blunt ends, moving the pickup elements radially inwardly in unison while continuing to apply said pressure and thereby causing an upward puckering of the top layer only of cloth into the space between the pickup elements, and pinching the puckered portion of the top layer of cloth with the pickup elements as they move closer together radially and then elevating the pickup elements in unison to lift the single layer of cloth from the stack.

18. in a cloth pickup apparatus, a cloth pickup head adapted to be raised and lowered relative to a supported stack containing multiple cloth layers, said head adapted to pick up the cloth layers individually and comprising plural circumferentially equidistantly spaced pickup fingers, each finger having a blunt leading tip adapted to contact the top of said stack under pressure and to force a small bulge in the uppermost layer of cloth only upwardly between the fingers while the fingers are separated, camming faces on the fingers, and coacting relatively movable camming means engaging the camming faces of the fingers and closing the fingers radially to reduce said space between the fingers and thereby pinch said small bulge of the top cloth layer, whereby said head may then lift the uppermost layer cleanly from the stack.

19. The structure of claim 18, wherein said fingers are four in number and include exterior circumferential conically tapered camming faces and each finger includes a pair of right angular interior sidewalls, said sidewalls of the fingers collectively producing intersecting right angular crossing slots between the fingers and said bulge entering said slots substantially at the intersection thereof. 

